When the rotor of a motor rotates, the active force exerted by the air on the vane attached to the rotor or changes in the direction of the electromagnetic force exerted on the rotor can make the rotor fluctuate or vibrates up and down. This causes the problems of noises, worn-out parts, or the like.
Referring to FIG. 4 that is a schematic view showing a conventional combination of a rotor structure and a stator. The rotor structure comprises a rotor case 41, a magnet 3, and a vane shell 4. The vane shell is substantially in the shape of a cup, with a plurality of blades formed around its outer side. The rotor case 41 is also in the shape of a cup and provided on the inner side of the vane shell 4. The magnet 3 is installed within the rotor case 41. The stator comprises a coil 5 and a silicon steel set 6. The rotor is coupled to the bearing 8 in the stator by the shaft 7. When the coil 5 of the stator is energized by a current, magnetic force is generated via the silicon steel set 6 and the magnet 3 of the rotor to cause the rotor to rotate.
The rotor case 41 and the magnet 3 keep a saturation state of magnetic balance. The magnetic field generated by the coil 5 induces a magnetic force on the magnet 3, but essentially has no magnetic interaction with the top of the rotor case 41. In other words, the magnetic force generated by the coil 5 has little influence on the rotor in the longitudinal direction of the shaft 7. The fluctuation or vibration of the rotor usually has been alleviated by an elastic member, such as a C clasp, a spring, or the like. Yet this type of design can only keep the static balance of the rotor. When the rotor rotates, there are still problems such as noise and wear of the C clasp.